Alan Tran

Improving resonance is not going to directly produce a natural vibrato, BUT... it is hard to have nice vibrato, without good resonance. Good resonance is one of the "ingredients" to getting vibrato to work and sound good.

Wow! Boyz ii Men and I didn't even get to hear it!
Who's part was it? Was it Shawn? Was it Wanya? 
 
Edit: It wouldn't play at first and I thought it said it was locked, but I heard it.
 
You have a good base, brother. If I would say anything, I would say to try to put more passion into it. The Boyz almost sound like they're crying when they sing this. And try to work on your runs.

Agreed.
There is a lovely voice here, but it isn't being utilized to its full aesthetic potential. Draven is correct on his point about resonance. You are resonanting too much in a lower position ( throaty )... with a little bit of good direction and practice, you can learn to lift your resonance to higher positions where it can sort of "float" more. A more "top down" resonance is more maneuverability of your voice because your resonance will not be tethered by the bulk of a more primitive, throaty position. The result of this will also be a much more beautiful timbre and sound color in your voice, in particular for this kind of singing in your sample.
Yes, my program The Four Pillars of Singing absolutely will help you if you choose to make a commitment to the training. 

You have  a great voice! Good choice of song too. However, most of your singing and resonance is being placed in your throat, in more of a speech mode. This will make higher nd lower notes more difficult, even if your more relaxed chest voice range is easy to control. It's also apparent in some of the dynamics of your plosives, the low level of breath suppport, and some of your curbing vowels (vowels resonating further back). You are, however, always on pitch in the more comfortable parts of that range.
What I hear you need is better resonant placement, more lifted to the soft palate and a bit forward. A bit more push or lockdown in the diaphram area (your solar plexus specifically) will support that better resonant placement and give your voice more body too. But that's only a start. One way to begin training yourself to resonate and support in this way is to start humming songs while buzzing your lips. This is called "Tracking". Another that I teach is to place a finger across your bottom lip and try to sing up and over it.
Are you training? Do you have a teacher? I highly suggest you check out the course, The Four Pillars of Singing, created by the owner of this forum.